Too Many Bases Exceed the Drive Budget - Semiconductor Physics and Transistor Switching Step by Step

Fanout fails when summed base current exceeds the driver limit.

Fanout fails when summed base current exceeds the driver limit. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.

highlighted = computed this step

Seven half-ampere bases need seven-halves amperes

Seven base inputs at 1/2 A each sum to 7/2 A.

7\cdot {1\over 2}\ \text{A}={7\over 2}\ \text{A}

Above the driver limit, the budget fails

The total 7/2 A is greater than the 3 A driver limit, so this fanout is rejected.

{7\over 2}\ \text{A}>3\ \text{A}